The invention relates to a pipe-drilling fitting for a medium-conveying pipe, comprising a housing which has a drilling stub, which can be fitted at an angle to the pipe axis, for drilling into the pipe wall, and a branch stub which is arranged at an angle to the drilling stub, a rotationally actuable cutting bush being arranged in the drilling stub, the cutting bush and the drilling stub having mutually complementary screw threads, and at least one sealing means for sealing the medium-conveying pipe with respect to the outside being provided between the drilling stub and the cutting bush.
DE 196 30 029 A1 has disclosed a pipe-drilling fitting in which the cutting sleeve has both a cutting function and a sealing function. The sealing function is provided by elastic sealing rings which are arranged in radial grooves on the outside of the cutting bush, in the region of an external thread, and slide along a complementary internal thread on the drilling stub. The internal thread extends over a length which is longer by a multiple than the thickness of the sealing ring. Over this length, the internal screw thread can easily cut into and damage the elastic sealing ring as the components are repeatedly screwed in and out. The great length also leads to a considerable overall height.
It is an object of the present invention to provide a pipe-drilling fitting which is as simple and compact as possible and exhibits a maximum possible sealing function in all phases of use.